The present invention relates to a reinforced flexible graphite sheet and, more specifically, relates to a flexible graphite sheet showing improved strength and gas permeability.
Heretofore, expanded graphite sheets have been prepared by compression-molding expanded graphite particles and used for heat-resistant packings, separators for use in fuel cells and the like.
However, since the conventional graphite sheets inevitably have minute hollows between compressed, expanded graphite particles in the sheet, the gas permeability can not be reduced to less than a certain value. Further, when such graphite sheets used, for instance, as a separator for use in fuel cells are in contact with liquid such as phosphoric acid, the liquid gets into the minute hollows, particularly, gaps as mentioned above and in result undesired phenomena of swelling the sheet are caused.
In addition, since the conventional graphite sheets have low scratch hardness, sufficient cares have to be taken upon handling them.
An object of the present invention is to solve the foregoing defects in the prior art.
An another object of the present invention is to provide a flexible graphite sheet having improved mechanical strength and low gas permeability and causing no undesired swelling of the sheet.